Packaging Applications

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Packaging Applications

Once a Java EE unit has been produced, it is ready to be deployed. Deployment typically
involves using a platform's deployment tool to specify location-specific information, such as a
list of local users that can access it and the name of the local database. Once deployed on a local
platform, the application is ready to run.

Packaging Applications

A Java EE application is delivered in an Enterprise Archive (EAR) file, a standard Java Archive
(JAR) file with an .ear extension. Using EAR files and modules makes it possible to assemble a
number of different Java EE applications using some of the same components. No extra coding
is needed; it is only a matter of assembling (or packaging) various Java EE modules into Java EE
EAR files.

An EAR file (see

Figure 16

) contains Java EE modules and deployment descriptors. A

deployment descriptor is an XML document with an .xml extension that describes the
deployment settings of an application, a module, or a component. Because deployment
descriptor information is declarative, it can be changed without the need to modify the source
code. At runtime, the Java EE server reads the deployment descriptor and acts upon the
application, module, or component accordingly.

There are two types of deployment descriptors: Java EE and runtime. A Java EE deployment
descriptor is defined by a Java EE specification and can be used to configure deployment settings
on any Java EE-compliant implementation. A runtime deployment descriptor is used to
configure Java EE implementation-specific parameters. For example, the Sun Java System
Application Server Platform Edition 9 runtime deployment descriptor contains information

application.xml

sun-application.xml

Assembly

Root

META-INF

Web

Module

EJB

Module

Application

Client Module

Resource

Adapter Module

FIGURE 16

EAR File Structure

Packaging Applications

Chapter 1 · Overview